Couple of things I'll raise to let you have a think about. 1st is the placement of the enlarger at the end. this will mean you have to turn to the trays and the amount of space you have is pretty narrow, even for a little guy. By putting it (maybe on the wall) where you've got the 'cutter' (which I think would be hard to use there as you'll be reaching across) you can then just shuffle left and right up and down the enlarger/tray line. By putting the enlarger on the wall you can have enough bench space for doing things, just have some shelves underneath to store your easels and cutter. you could probaly put a paper safe to the left next to the HWS.
The 2nd one is your sink. Not sure how you intend to construct your plywood sink, but if it involves a frame, your going to waste a lot of valuable space. An alternative would be to make your sink out of plastic sheeting. Going by my own setup (http://www.apug.org/site/main/album_page.php?pic_id=83), the sink only really needs to be an bench top with the luxury of sides in case you spill something as your chemicals are in trays and I doubt you'll ever want to fill the sink anyway. I had my sink made but in hindsight I should have done it myself and saved a packet. It's only glued together, with a bead of silicon for waterproofing. I specified 100mm sides but in reality 1/3 or 1/2 that would be ample. I have a well at one end with the drain. This area is flat which combined with the drain that sits proud (I didn't realise it at the time and with the plumber standing there at $$$/hr didn't have time to do anything about it) so the last bit of water doesn't run out, at the end of a session I sponge it out. One day I'll modify it so it's recessed somehow.
Anyway... The upside of this is since the plastic is 5mm think, you don't eat up valuable space. If you want to see a better pic of the sink or the plans I drew for my sink (which will explain the well end better) yell out and I'll send them. (ohh the plastic sheet was heaps cheaper though the plastic fabricator I had make the sink than a hardware store when I went and got some for my splashback)
phew.. glad I didn't have a lot to say